1. Field of the Invention
The invention relates to a splined annular member for use as a component in various types of machines.
2. Description of the Related Art
Machines, such as vehicular automatic transmissions and the like, incorporate many annular members having a splined annular inner peripheral surface, the splined surface having an arrangement of alternating inwardly protruded ridges and troughs formed between the ridges. Since these splined annular members are used as rotating members, it is desirable that the splined annular members retain high rigidity even during high-speed rotation.
With conventional splined annular members, it is a common practice to increase the plate thickness of the spline or the like, in order to improve rigidity of the member. However, this conventional strategy for improving rigidity of an annular member, by increasing the wall thickness, also increases the weight and size of the member, and therefore cannot meet demand for weight and size reductions.
Japanese Patent Application Laid-Open No. SHO 63-52257 describes a splined annular member for use as a clutch drum. This patent application discloses a splined annular member as shown in FIG. 6 in which a side wall 21 is deformed into a step (“overhang”) without breakage to form surface 931. Another wall 932 of the snap ring groove is formed by half blanking. This improves rigidity, as compared with a design in which the two walls of a snap ring groove are formed with a breakage. However, the stepped wall increases the total width of the snap ring groove, and therefore reduces the effective area of the splines. Furthermore, in a clutch drum, the design of FIG. 6 does not provide adequately stable retention of the snap ring.